A horsey riddle

Here is a little mystery for you all to try to solve.

Frostie lives in a pipe stall on the edge of the arena. She has been out here for months, although until recently, she was in a much larger stall. It turns out the panels were owned by a client and they wanted them back. This is the place.

One Monday evening, she was fine. The next morning, she was not fine. As a matter of fact, she looked like she'd been hit by a truck. NOTE: The pictures below were all taken two weeks after the incident.

Both front legs were scraped on the front AND back.

Her elbow looked as though it had received a friction burn.

So had her withers (on the same side as her elbow).

Her withers are still swollen and we're hoping she didn't break them.

Tina guessed that she had gotten cast in her stall at some point, and injured herself trying to get free. It's fairly common with horses, that they lay down too close to a wall or other boundary, then can't get any leverage to get back up again and thrash about in the process.

Here's what I don't understand: How the hell did she get her withers involved?

One view of ties and pipes.

As you can see, Tina put railroad ties around the stalls to keep the bedding from leaking out. I wondered why none of them was damaged or moved in her struggle, but Tina said she puts spikes down to keep them from moving (she has since removed the spikes so they can be pushed out of the way if a horse gets stuck).

But still... her withers?

Another view of ties and pipes

It doesn't make sense to me. Can anyone out there provide a scenario? I'm stumped.